Process for recovering hydrocarbons from underground formations



July 26, 1960 1- ETA 2,946,382 PROCESS FOR RECOVERING HYDRO BONS FROMUNDERGROUND FORMATI Filed Sept. l9, l9

INVENTORS M R. TEK A F BERTUZZI ATTORNEYS United States Patent PROCESSFOR RECOVERING HY DROCARBONS FROM UNDERGROUND FORMATIONS Mehmet R. Tekand Andrew F. Bertuzzi, Bartlesville,

0kla., assignors to Phillips Petroleum Company, a corporation ofDelaware Filed Sept. 19, 1956, Ser. No. 610,753

8 Claims. (Cl. '166-11) This invention relates to a process forrecovering hydrocarbons from porous underground formations containingcarbonaceous material.

The recovery of oil and. other hydrocarbons from underground porousformations containing carbonaceous materials, such as oil and coal, byin situ combustion and by hot fluid drive utilizing hot gases and/or hotliquids is currently being emphasized as a production technique. Aconventional in situ combustion method comprises initiating combustionof the oil adjacent a bore hole in the formation by any suitable meansand injecting air through the bore hole into the formation so as todrive the combustion zone or front radially and laterally outwardly fromthe bore hole. A recent development in in situ combustion technique inthe field, of oil recovery is disclosed and claimed in the copendingapplication of John W. Marx, Serial No. 526,388, filed August 4, 1955,and comprises, establishing a combustion zone around a production wellby conventional methods so as to provide a combustion zone and a heatreservoir of sufficient extent and temperature to permit cutting off thedirect flow of air through the production well and injecting air intothe formation through one or more spaced-apart Wells from the productionwell so as to cause the air to flow to the combustion zone at theproduction well and support combustiontherein so that the combustionfront is advanced countercurrently. to the flow of air toward theinjection well or wells. This technique is designated inverse airinjection in situ combustion as opposed to direct air injection throughthe well or bore hole around which combustion is initiated.

Another recent development in recovery of oil by in situ combustion isdisclosed in the copending application of I. C. Trantham and A. R.Schleicher, Serial No. 529,916, filed August 22, 1955, and comprisescontinuing the injection of air through one or more injection wellsafter the combustion front has'been advanced, by inverse air injection,to the injection well or wells so as to reverse the movement of thecombustion front and drive the same back through the formation to theproduction well around which combustion was originally initiated. Inthis technique, designated thermal echo, the returning combustion frontfeeds on the residual carbon deposited in the formation during theinverse air injection phase of the process.

Oil recovery has also been effected by injecting hot combustion gasformed at ground level and/or superheated steam into a formation thru awell bore therein and the hot fluid is then driven thru the formation byfluid pressure so as to drive hydrocarbons from the forma tion thru aproduction well.

In these various production techniques an important problem is theconservation of heat in order to avoid unnecessary costs in the recoveryof hydrocarbons. Substantial amounts of heat are lost to the overlyingand underlying strata adjacent a carbonaceous formation and it is withthe reduction and minimizing of these heat losses that this inventionisconcerned.

. the borehole.

" ice Hence, it is an object of the invention to provide a process forrecovering hydrocarbons from a porous underground formation containingcarbonaceous material with a minimum of heat loss to the surroundingstrata. Another object is to provide a more effective method ofrecovering hydrocarbons from an underground formation. A further objectis to provide an oil recovery process which recovers hydrocarbons moreefliciently and at a faster rate from a porous oil-bearing formationthan is possible by other production methods. Other objects of theinvention will become apparent from a consideration of the accompanyingdisclosure.

The invention comprises fracturing a porous or fluid perviousunderground formation containing carbonaceous material, such as oil, ata level adjacent the center of the formation around a well therein andalso fracturing the formation at higher and lower levels around one ormore surrounding wells. The recovery of oil or other hydrocarbon fromthe formation is then effected by introducing hot fluid into thefracture adjacent the center of the formation and driving the hot fluidupwardly andv downwardly therefrom to the higher and lower levelfractures so as to drive hydrocarbons from the formation. While thepreferred technique involves establishing a combustion front in thefracture at the center of the formation and advancing the combustionfront upwardly and downwardly therefrom so as to produce oil and otherhydrocarbon from the formation, it is also within the scope of theinvention toutilize hot gases and hot liquids heated. andinjected fromthe ground level or from within It is also feasible to effect the hotfluid drive fromvthe upper and lower fractures toward' the intermediatefracture but the heat losses to the overburden and underlying strata aregreater with this type of recovery.

-A more complete understanding of the invention and, particularly,further embodiments thereof may be had from a consideration of theaccompanying drawing which is a schematic elevation of an arrangement ofwells and fractures in an underground formation for the recovery ofhydrocarbon in accordance with the invention.

Wells 10, 12, and 14 extending into the earth from the surface 15penetrate a porous oil-bearing formation 16 below overburden 18 andabove formation 20. One or more fractures 22 and 23 are formed inconventional manner by perforation of the casing in well 12 at thedesired level and pumping fluid into the formation in suflicient volumeand at a sufficient rate to effect the desired horizontal fracturing.Fine, strong, granular material, such as sand, metal particles, and thelike, are introduced to the fractures with the fracturing fluid injectednear the end of the injection step so as to prop the fractures open.Fractures .26, 2'7, and 23. are then induced in the formation thru wells10 and Mat levels above and below the level of fractures 22 and 23 sothat a second group of fractures overlap the fractures effected,

thru well 12, Well 12 is imperforate at other levels than the level offractures 22 and 23 and wells 10 and 14 are perforate only at the levelof the fractures 26, 27 and 28 so that fluid under, pressure inducedthru wells 10 and 14 must pass generally vertically thru the formationin wells 10 and 14; and fractures 26, 27, and 28 extend' to theproximity of or to the area adjacent well 12.

The preferred method of operation is to' initiate combustioninfractures22-- a-nd/ or '23 by conventional means and then drive the combustionfront or zone substantially vertically thru the formation to theadjacent fractures leading to wells and 14. In this manner the heatdeveloped in the formation and the hot fluid drive produces hydrocarbonfrom the formation which is recovered either from wells 10 and 14 orfrom well 12 depending upon whether direct or inverse injection isutilized. If inverse injection is made use of, air is injected thruwells 10 and 14 so that it passes thru fractures 26, 27, and 28 andthence thru the formation of fractures 22 and 23 and to the combustionfront established therein whereby the combustion front is advancedcounter-currently to the flow of air so that it eventually arrives atthe fracture at which air is being introduced to the formation. In otherwords, the combustion front established along fractures 22 progressesupwardly to fracture 26 and downwardly to fracture 27. -If additionalfracture 23 is utilized, the combustion front established there isadvanced upwardly to fracture 27 and downwardly to fracture 28. In thismanner a substantial proportion of the hydrocarbons in the formationbetween the fractures is produced leaving a coke residue which can beburned out by continuation of air injection after arrival of the frontat the injection fracture so that the front travels back to the fracturefrom which it originated, thereby producing the reminder of the oil inthe formation (of course, less the amount of hydrocarbons consumed bythe combustion process). The use of a plurality of fractures surroundingwell 12 and overlapping fractures around wells 10 and 14 makes efficientrecovery of the hydrocarbons possible with a minimum of heat loss to theoverlying and subjacent strata. The more rapid recovery of oil effectedthru the system shown in the drawing also contributes to the decrease inloss of heat to the surrounding non-oil-bearing formations.

'It is also feasible to initiate combustion in fractures 26, 27, and 28and inject air thru well 12 into fractures 22 and 23 so that thecombustion front moves downwardly from fracture 26 both upwardly anddownwardly from fracture 27 and upwardly from fracture 28 to theadjacent fractures 22 and 23.

In case recovery is to be elfected by injection of hot fluid from theground surface, it may likewise be introduced either thru wells 12 and14 or thru well 10, but in order to minimize heat losses to thesurrounding strata it is advantageous to inject the hot fluid thru well10. Utilizing this technique hot combustion gas, hot water, superheatedsteam, and any other hot fluid nondeleterious to the hydrocarbon in theformation and to the equipment may be utilized. It is also feasible toheat the injection fluid by means of a heater (electrical or gas) placeddownhole. Of course, any type of heat source may be utilized to heat theinjection fluid.

Certain modifications of the invention will become apparent to thoseskilled in the art and the illustrative details disclosed are not to beconstrued as imposing unnecessary limitations on the invention.

We claim:

1. A process for recovering hydrocarbons from an underground permeableformation containing combustible carbonaceous material comprisingproviding in said formation a first well and a plurality of wellssurrounding said first well, all of said wells extending to and beingcased to a lower section of said formation; perforating the casing insaid first well at an intermediate level of said formation andfracturing said formation horizontally thru the resulting perforationsin said casing to form an intermediate fracture extending to areasadjacent the casings of the surrounding wells; perforating the casingsin said surrounding wells at levels above and below said intermediatelevel and fracturing said formation horizontally thru the resultingperforations in said casings to an area adjacent said first well to formupper and lower fractures so that the fracture systems overlap and sothat the fracture systems around said surrounding wells communicatedirectly with said wells and are sealed from said first well and thefracture system around said first well communicates directly with saidfirst well and is sealed from said surrounding wells; propping theaforesaid fractures open; initiating combustion in said formation alongthe fracture communicating with said first well; feedingcombustion-supporting gas into the resulting combustion zone thru atleast one of said wells so as to move same toward both said upper andlower fractures; and recovering from at least one of said wellshydrocarbons driven from the formation by the combustion.

2. A process for recovering hydrocarbons from an underground permeableformation containing combustible carbonaceous material comprisingproviding in said formation a first well and a second well, both beingcased to a lower section of said formation; perforating said first wellat an intermediate level of said formation and horizontally fracturingsame thru the resulting perforations to form an intermediate fractureextending to an area adjacent said second well; perforating the casingof said second well at levels above and below said intermediate leveland horizontally fracturing said formation thru the resultingperforations to an area adjacent said first well to form upper and lowerfractures so that the resulting fracture systems overlap and so thatsaid first well is sealed from the fractures made thru said second welland said second well is sealed from the fracture made thru said firstwell; initiating combustion in said formation along the fracturecommunicating with said first well; advancing the resulting combustionzone both upwardly and downwardly toward said upper and lower fracturesaround said second well by passing combustion supporting gas to saidzone thru one of the wells; and recovering from the other of the wellshydrocarbons driven from said formation by the combustion.

3. The process of claim 2 wherein said combustion zone is advanced byinjecting air thru said upper and lower fractures and recovery is thrusaid first well.

4. The process of claim 2 including reversal of said combustion zoneafter it reaches the upper and lower fractures by continued airinjection thereby driving same back to said intermediate fracture so asto recover additional hydrocarbon from the formation.

5. The process of claim 1 wherein said combustion zone is advanced byinjecting air thru said upper and lower fractures so as to effect flowof air countercurrently to movement of the combustion zone, andcombustion gases and hydrocarbons are removed thru said intermediatefracture.

6. The process of claim 5 including reversal of said combustion zoneafter it reaches said upper and lower fractures by continuing said airinjection thereby driving same back to said intermediate fracture.

7. The process of claim 1 wherein said combustion zone is advanced thrusaid formation by direct air injection thru said intermediate fracture.

8. The process of claim 2 wherein said combustion zone is advanced thrusaid formation by direct'air injection thru said intermediate fracture.

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